C34-24 Thymic Stromal Lymphopoietin (TSLP) Mediates Airway Inflammation and Senescence in Asthma

Abstract Rationale Asthma impacts 10% of the world’s population, often resulting in exacerbations and loss of productivity from school and work, and totaling over 81B annually in health care costs in the US alone (GBD 2015 Chronic Respiratory Disease Collaborators. Lancet Respir Med. 2017; Nurmagambetov T, et al. Ann Am Thorac Soc. 2018). Recurrent episodes of inflammation and dysregulated airway repair over time result in loss of lung function due to epithelial thickening, subepithelial fibrosis, inflammatory cell proliferation, and mucus hypersecretion. Another important process that occurs in response to airway injury is cellular senescence, a process of irreversible cell cycle arrest that can become pathological over time. Senescent cells have lost replicative capacity but can continue to produce cytokines and growth factors that sustain inflammation and impair epithelial integrity, also referred to as the senescence-associated secretory phenotype (SASP). Numerous stressors such as pollution, smoking, and allergens are known to cause increased airway inflammation and senescence through production of TSLP by the airway epithelium, which activates cell cycle arrest. This study seeks to determine whether TSLP promotes airway remodeling and senescence in asthma. Methods Asthmatic and non-asthmatic participants underwent bronchoscopy with endobronchial brushings as previously described (Francisco D, et al. J Immunol. 2020). Primary bronchial epithelial cells (BECs) were cultured on Transwell™ plates at an air-liquid interface for 21 days. Cells were then treated with TSLP (with doses ranging from 10 to 200ng/ml in the apical, basolateral, or both compartments for 6 or 24 hours). Quantitative RT-PCR was performed to measure markers of mucus secretion (MUC5AC, MUC5B), inflammation (eotaxin-2, TSLP), and cell cycle arrest and senescence (Ki67, p14, p16, p21). Senescent cells were identified via confocal microscopy using the CellEvent™ Senescence Green Detection Kit (Thermo), a fluorescence-based assay for SA-β-galactosidase activity. Results In BECs obtained from asthmatic and non-asthmatic participants, TSLP treatment significantly increased expression of markers of mucus secretion, inflammation, cell cycle arrest, and senescence (p 0. 05). These effects were seen most consistently with basolateral application of TSLP, and not with treatment in the apical compartment or both compartments. SA-β-galactosidase activity appeared to be more prominent in treated BECs obtained from non-asthmatic participants. Conclusions TSLP is a key mediator of inflammation and cellular senescence in asthmatic and non-asthmatic BECs. Future experiments will seek to determine whether these effects can be attenuated by innate immune modulators. This abstract is funded by: NIH U19AI125357 and U54AG075936